For purposes of this application, a read or write operation of information to a magnetic tape is referred to in general as a "read-write" operation.
Data, programs, and other information are often read or stored to a magnetic tape (tape) by the use of a tape transport machine ("transport machine") that is able to perform read-write operations to the tape. Typically, these transport machines include one or more read-write heads and make use of two reels to transport the tape. In order to perform read-write operations to the tape, the tape is wound onto one reel while unwound from the other reel in a manner so that the tape is controllably moved through a guide positioned between the reels and in proximity to the heads.
Some transport machines are designed to operate with tape from a tape cartridge. When the tape cartridge is loaded, the transport machine can interface with tape in the cartridge in order to perform the desired read-write operations. After performing these operations, the transport machine allows the tape cartridge (with the tape) to be unloaded.
One common type of tape cartridge (alternatively referred to herein as a "single reel cartridge") houses tape wrapped onto a single reel (alternatively referred to herein as the "source reel"). Typically, transport machines designed to accept a single reel cartridge include a take-up reel and threading apparatus. Upon loading the cartridge into the transport machine, the threading apparatus operates to thread the tape appropriately through the transport machine and establish a connection with the take-up reel. Further transport of tape is then accomplished by the coordinated winding and unwinding of tape onto the take-up reel and source reel.
As is known in the art, it is highly desirable that the winding substrate (referred to herein as the "take-up reel winding substrate") for tape wrapped onto a take-up reel be acceptably smooth so that irregularities are not created in the tape. Irregularities in the tape can make read-write operations to the tape less reliable, especially in the area where the irregularity is present. In the case of high storage capacity tapes wherein data density on the tape is high, even a small irregularity can affect the reliability of a large amount of read-write operations to the tape.
One popular technique for threading tape from a single reel cartridge makes use of a leader block permanently connected to the free end of the tape in the cartridge. During a threading operation of a loaded single reel cartridge, threading apparatus (see, for example, U.S. Pat. No. 4,335,858 incorporated herein by reference) residing in the transport machine operates to move the leader block out of the cartridge and through a threading path in the transport machine in a manner so as to thread the tape. The threading apparatus further operates to insert the leader block into a slot in the take-up reel. When the leader block is so inserted, an exposed curved surface of the leader block and the outer cylindrical surface of the take-up reel form the take-up reel winding substrate. Thus, the smoothness of the take-up reel winding substrate is in part a function of a component (i.e., the tape cartridge leader block) of the loaded cartridge.
Typically, transport machines that make use of the threading technique just described can operate with single reel cartridges from a wide range of manufacturers. These manufactures may or may not include leader blocks in their tape cartridges that provide for an acceptably smooth take-up reel winding substrate. This situation can create unacceptable variations in transport machine reliability that are outside the control of the transport machine manufacturer.